New ternary powder metallurgy Ti alloys via eutectoid and isomorphous beta stabilisers additions.

A group of new ternary Ti alloys bearing eutectoid and isomorphous beta stabilising elements was created to be manufactured through the conventional powder metallurgy route. The effect of the simultaneous addition of the same amount of Mn and Nb on the manufacturability, properties, and hardening behaviour was investigated. The ternary alloys are composed of the α-Ti and ß-Ti phases and have a lamellar microstructure resulting from the slow cooling upon sintering. However, the size of the equiaxed α grains and of the α + ß lamellae is monotonically reduced, especially the interlamellar spacing, as the amount of alloying elements increases. Due to their physical properties, Mn enhances and Nb hinders densification during sintering resulting in a decreasing trend of the relative density with the alloying elements content. Consequently, the resistance to plastic deformation increases (UTS, 514-726 MPa), the ductility decreases (elongation, 13.2-2.6%), and the fracture mode changes from intergranular to transgranular. The new ternary alloys share the same hardening mechanism, but the amount of deformation after necking is, generally, higher for lower amounts of Mn and Nb.

Fabrication and characterisation of low-cost powder metallurgy Ti-xCu-2.5Al alloys produced for biomedical applications.

Ti and Ti-based materials are of growing interest as biocompatible structural materials in a wide range of biomedical applications. Traditionally, one of the main factors hindering the wider use of this class of materials has been the relatively high manufacturing cost. Today, Ti-6Al-4V remains the most widely used material for dental and orthopaedic implants. However, the presence of cytotoxic vanadium in its composition casts doubt on the safety of using this alloy as biomedical material. This study aims to study the microstructural features and mechanical properties of ternary alloys Ti-xCu-2.5Al (where x = 0.5-5 wt%Cu) obtained by powder metallurgy (PM) methods. The attractiveness of this group of materials lies in its economy due to the significantly lower cost of Cu compared to vanadium and the intrinsic advantages of PM. The obtained samples demonstrated increasing tensile strength and Vickers hardness values with increasing Cu content, from 640 MPa to 195 HV to 800 MPa and 250HV, respectively. At the same time, an inverse relationship was observed for the elongation. A higher content of ß-stabiliser is accompanied by the formation of a more significant number of spherically shaped pores and a refined lamellar structure which are responsible for the changes in mechanical properties.

Ternary Ti alloys functionalised with antibacterial activity.

Prosthesis bacterial infection occurring during surgery is a rising health issue. Pathogenic bacterial infection causes inflammation, interferes with the healing process, inhibits osteogenesis and, eventually, leads to implant failure. These issues can be tackled either by applying coatings or developing multifunctional (i.e. structural and antibacterial) materials. In this work, ß eutectoid bearing functionalised Ti alloys were designed and manufactured via the cost-effective press and sinter powder metallurgy route. The systematic analysis of the ternary Ti-xCu-yMn alloys shows that the mechanical properties proportionally increase with the amount of alloying elements added. All the ternary Ti-xCu-yMn alloys have strong antibacterial activity against Escherichia coli with respect to the negative control (i.e. pure Ti). Our study demonstrates that ternary Ti-xCu-yMn alloys are promising candidates for structural prostheses functionalised with antibacterial capability.

Behaviour of novel low-cost blended elemental Ti-5Fe-xAl alloys fabricated via powder metallurgy.

Ti alloys, generally made via wrought metallurgy, are commonly used as biomedical materials. The manufacturing of such alloys via powder metallurgy offers the possibility to reduce the cost as well as to develop innovative compositions not otherwise achievable. The aim of this study is to understand the effect that the progressive addition of Al has on the physical and mechanical behaviour of the low-cost powder metallurgy Ti-5Fe alloy for structural biomedical implants. Specifically, Ti-5Fe-xAl (x = 1-6 w.%) alloys were developed combining blending elemental and cold pressing plus vacuum sintering to further limit the manufacturing costs as Al is lighter and cheaper than Ti. This investigation demonstrates that the amount of Al added significantly changes the thermodynamics of the sintering process and induces microstructural modifications such as grain refinement. These effects jointly with the Al solid solution strengthening leads to progressively stronger and harder (but less ductile) α+ß Ti alloys characterised by the typical α+ß lamellar microstructure with mechanical behaviour suitable for a variety of structural biomedical implants.

Low-cost powder metallurgy Ti-Cu alloys as a potential antibacterial material.

Ti and Ti alloys are extensively used in biomedical applications due to their excellent biocompatibility and mechanical properties but their high-cost of production is still a limiting factor. It has been reported that the addition of Cu to Ti enables the creation of Ti alloys exhibiting antibacterial properties. Therefore, in this study Ti-Cu alloys (Cu = 0.5, 2.5 and 5 in wt.%) with potential antibacterial activity were fabricated by powder metallurgy (i.e. cold press and vacuum sintering) to reduce the production costs. As many biomaterials are employed as structural components, the Ti-Cu alloys were also subjected to ß forging in order to improve their mechanical properties. It is found that the studied Ti-Cu alloys have superior mechanical properties to other commonly used Ti-based materials and are, thus, potential candidate for biomedical applications. Moreover, among the tested materials, the ß forged Ti-5Cu alloys has tensile strength of 904 MPa, elongation of 6.7%, and Vickers hardness of 302 HV, which are comparable to those of the Ti-6Al-4V, and comprises the Ti2Cu phase (confirmed by the XRD) as microstructural feature, which is fundamental to guarantee antibacterial properties.

Mechanical properties and microstructure of Ti-Mn alloys produced via powder metallurgy for biomedical applications.

Titanium and especially its alloys are highly employed materials in biomedical applications because of their balanced mechanical properties and biocompatibility. Ti-Mn alloys (1, 5, and 10 wt%. Mn) were produced by powder metallurgy as a potential alternative material for biomedical applications. Two sets of samples were produced, one set as-sintered and the other was beta (ß) forged. For the as-sintered samples with a content of up to 10 wt% Mn, the tensile strength ranged from 606 to 1070 MPa. On the other hand, for the ß forged alloys the tensile strength ranged from 728 to 1224 MPa and the maximum value was for Ti-5Mn. Forged Ti-5Mn exhibits a good balance of mechanical properties such as ultimate tensile strength (1224 MPa), elongation (4.6%) and Vickers hardness (415 HV). The purely elastic properties of the Ti-10Mn alloy is attributed to the effects of the omega (ω) phase, the formation of which is due to the high amount of beta stabiliser added to Ti.